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Monday, June 3, 2013

Roundup is Roundup…Right?

Tony Koski, Extension Turf Specialist

Which one do I use? They both say Roundup!

If you are reading this in hopes that the turf specialist
has seen the light and jumped on the Occupy Monsanto bandwagon, well…you can
stop reading now. Glyphosate/Roundup is still, in my opinion, one of the most
effective, inexpensive, easy-to-use and safest herbicides available to the home
gardener – and to professional weed managers as well. But a stroll through the
pesticide aisle of any hardware store or big box garden center can present to
even the sharpest of gardeners a somewhat bewildering selection of Roundup
products from which to choose…Roundup Concentrate…Roundup Concentrate
Plus…Roundup Extended Control. The various Roundups entice you with promises
like “Results in 12 hours” (faster is always better…right?) or “Controls weeds
for up to 4 months” (longer is always better…right?). And then there is yet another
glyphosate-containing product, ominously named GroundClear, which provides one
year or more of weed control (REALLY longer is BEST…right?). It’s easy to
understand the confusion when asking oneself “Which one do I buy?”. And I
suppose it’s somewhat easy to understand when consumers (professional
applicators don’t get a break here) misuse these products in the landscape –
although a thorough reading of the label would, in most cases, prevent some
damn dumb mistakes. (What? Read a label? Ain’t nobody got time for that!). Sooo….how
different are these Roundup products? Can they be used interchangeably? Is one
better than the others? Are all of them “safe” for home landscapes?

First, the traditional verbiage – to protect my you know
what – whenever we Extension types write about pesticides: READ THE LABEL
before purchasing, much less using, any of these products! A reading of the
ingredients section of the various Roundup products demonstrates that they
aren’t the same. And while the "where to use/not to use" instructions aren’t always
the most clearly written, a close reading (ok, maybe 2 or 3 times…) of the label
will help prevent misuse of these products.

Roundup Super Concentrate
(white bottle…purple cap) is your good ol’ pure and simple glyphosate. Use it wherever (wherever the label allows,
that is…yes, READ THE LABEL!) you need non-selective control of weeds in your
landscape. It is taken up only by leaves and other above-ground green plant
tissue. No soil residual. No root uptake. No extended control. This Roundup can be safely used: on your
driveway or sidewalk or patio…on mulch circles around trees (but don’t spray
the trunk, or surface roots, or suckers)…to renovate your lawn…or to kill a section
of your lawn and replace it with a flowerbed or veggie garden. This is the
slowest acting Roundup product, taking anywhere from 5-10 days before you begin
seeing symptoms that the weeds are dying. But because we are so impatient (we “need”
FASTER internet… FAST food…RAPID transit…INSTANT mashed potatoes), a couple of
other Roundup products were developed to satisfy consumer demand for more rapid
weed kill. Enter Roundup Plus…

Faster Roundup is better....isn't it?

Roundup Concentrate
Plus (white bottle…red cap) contains glyphosate and another herbicide
called diquat dibromide. The diquat is added to give a more rapid burndown of
weeds that have been sprayed. Other than providing the more rapid (within about
12 hours during hot weather) visual symptoms that the weeds have been sprayed,
this Roundup product works the same way as the basic concentrate. All foliar
absorption, no root uptake or soil residual. No extended control.

Roundup Ready-to-Use
Plus (blue and white bottle) contains glyphosate and pelargonic acid. The
pelargonic acid makes this Roundup product work even more quickly than the
Roundup Concentrate Plus – you may see wilting within 3 hours on a hot, sunny
day. So, for the VERY impatient, this Roundup product works even more quickly
than the Concentrate Plus product – but is otherwise the same: all foliar
uptake, no root uptake, no soil residual, no extended control. Use it the same
way you would the above two Roundup products.

Roundup Extended
Control (gray bottle) contains pelargonic acid (for rapid burn down) and a
herbicide called imazapic. Imazapic is added to provide the “extended control”.
It works as a preemergence herbicide to provide 3-4 months of weed control by
killing germinating seeds/seedling weeds. However, imazapic also is somewhat
root active and can provide postemergence control of some weeds as well. This is
where things get tricky. Imazapic is fairly water soluble, so it can move in
soil. This means it can move to parts of the landscape where you haven’t
sprayed it (down slopes, for example…or when sprayed on gravel-covered plastic).
And because of the long soil residual, don’t use this product where you may
want to plant something in the near future (so this one is a no-no for lawn
renovation, nor should it be used where you plan to plant a veggie or flower
garden in the future…or trees or shrubs).
The label does allow use over the root zone of trees and shrubs
(established ones…not newly planted), including on mulch circles around trees.
However, imazapic has been shown to cause injury to a

few tree species which
are sensitive to it: lindens, green ash, and cherry trees. Soooo….while it is
generally safe to use in those parts of the landscape where you need control of
existing weeds AND desire some long term weed control/prevention, you have to
recognize the potential for this stuff to “move” in the landscape. Use the same
precautions that you would with any Roundup product…and maybe consider if you
REALLY need to use this over the root zone of your trees?

And then there is GroundClear….While
it doesn’t have Roundup prominently displayed on the label, this is another
Roundup product. It is aggressively marketed on the radio and in the aisles of big
box stores. Who wouldn’t want weed control for a year - or longer? This is the
one where the “Keep out of reach of children” line on the label maybe should
read “Keep out of reach of adults who don’t read a label”. This Roundup product
contains imazapyr (a close relative of imazapic…see above), which is a VERY
long-lasting, soil/root-active herbicide. Imazapyr can last a year or longer in
soil, depending on soil type and how much moisture the soil receives. It is
non-selective, can move with water in soil, and is easily taken up by roots of
trees (yours or your neighbor’s), shrubs, vines, flowers, veggie plants,
turf….you get the idea. As the name would imply, this product really does
“clear the ground” on which it is applied. In my opinion, there are few places
in a home landscape where this product could be safely used. I doubt that there
is a driveway, patio, or fence line in any urban landscape that doesn’t have a
tree or shrub root growing under it. Unfortunately, the promise of long-term
weed control is so irresistible, it is bought and used in places where there is
significant potential for damage to trees and other desirable landscape plants.
This is one that you want to avoid using in your landscape, unless you REALLY,
REALLY know what you are doing – and even then I would be hesitant to use it. I have visited landscapes where professional
applicators (who should know better…and who violated the label by using it
where they shouldn’t have) have killed or injured dozens of trees using this
and similar products for mulch circle weed control.

Trees killed by improper use of herbicide containing imazapyr.

Like most things in life - when preventible, bad things happen - you can only blame yourself for
not reading (or following) instructions and heeding warnings. When you purchase any pesticide, you enter into a legal agreement that you will use it as the label
instructs. Your trees and turf can’t read the label…they trust that you will.

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The best way to kill honeysuckle bushes is to cut down the bush and immediately paint the cut stump with concentrated roundup, undiluted. Immediate means within a minute or two, preferably within 30 seconds of clipping or sawing the stem. 5 minutes is too late. Use a foam paint brush or a small hand sprayer pumped up just enough to dribble out liquid onto the cut part of the stump. The idea is for the capillaries in the live part of the wood just inside the bark to transport the herbicide directly to the roots. This works for Privet hedge bushes, too.

Manufacturers have a tough time writing comprehensive label guidance because of the economic impracticality of testing a new active on every species, every imaginable soil type, with every available adjuvant, in every conceivable climate and seasonal weather variation . . . you get the idea. In my experience, they tend to be overly optimistic with use sites. It is great to see this kind of real-world information, especially with such a digestible write-up. Nice work.

Some guy called to harp on me the other week because I haven't abandoned Glyphosate entirely, but he misunderstood my article page was meant to reduce chemical use. Some people pull their hair out over this one:

http://www.mdvaden.com/lasagna_gardening.shtml

As for Roundup, I find one particular huge advantage of the Vinegar realm and the sort. Its when a small weed tree had germinated and grown its roots into the root system of a shrub. If the weed tree is bent, sprayed and shaken dry, it will grow the herbide only into its own roots like small special operations forces chasing it down but protecting the desireable.

Some guy called to harp on me the other week because I haven't abandoned Glyphosate entirely, but he misunderstood my article page was meant to reduce chemical use. Some people pull their hair out over this one:

http://www.mdvaden.com/lasagna_gardening.shtml

As for Roundup, I find one particular huge advantage of the Vinegar realm and the sort. Its when a small weed tree had germinated and grown its roots into the root system of a shrub. If the weed tree is bent, sprayed and shaken dry, it will grow the herbide only into its own roots like small special operations forces chasing it down but protecting the desireable.